The present invention relates generally to improved building materials, and more specifically, to concrete construction units having enhanced structural values, including load bearing properties and resistance to fracturing. Porous mat-like structures subdivided into adjacent, cyclindrically shaped concrete bodies provide a highly versatile and economic unit of construction which can be used in fabricating wall panels, building foundations, domes and roofing; poles, pillars and bridge supports; pavement and floor construction, including beds for roads, driveways, foundations for waste disposal sites, etc. Such structures exhibit flexural characteristics , and therefore, have residual strength and extended life expectancies.
In fabricating concrete monolithic structures, such as walls, panels, pavements, support columns, etc., generally two steps are customarily followed. The first involves pouring a concrete mass into a form, followed by stripping the form once the mass has set-up. Concrete forms, however, are costly and labor intensive in fabricating and stripping. Monolithic, homogeneous concrete masses prepared from poured concrete are also structurally vulnerable to changes in weather, including rain, temperature extremes, frost upheaval; shock and natural disasters like tremors, earthquakes, etc., and because poured concrete lacks the ability to flex under stresses of load and impact, fractures can lead to early failure. For example, tank farm pads which support very heavy loads of gasoline, oil, chemicals, etc., are subject to freeze upheaval and impact. Consequently, conventional monolithic concrete pads are subject to fracture, and because residual structural values may be lacking will continue to striate, leading to instability and potential for leaking contents from storage tanks.
Because of the sensitivities of monolithic poured concrete structures unit size limitations become necessary to minimize the effect of fractures. Heretofore, whenever expanse and size of poured concrete structures exceeded minimal proportions, expansion joints, steel reinforcements, etc., were required. While the strength of concrete can be improved by reducing the ratio of mixing water to cement this approach has proven to be of little actual value because flow properties and placement of poured concrete can be adversely affected.
Others have attempted to fabricate improved concrete construction units by encasing concrete mix in flexible containers. U.S. Pat. No. 3,922,832 (Dicker), and U.S. Pat. No. 2,095,989 (Lillard) each disclose individual sack type construction units containing dry concrete mix. The Lillard patent discloses a sack fabricated from thin, inexpensive cloth, such as cotton muslin or cheese cloth preferably soaked in paraffin as a moisture barrier for the dry mix during storage. However, the wax barrier restricts the amount of water entering the sack at the time of hydration, and consequently, each sack must be perforated in order to hydrate the mix. Lillard also describes individual concrete sacks without a paraffin moisture barrier, but because of the overall bulk size of the filled sacks manual kneading is required to insure the cement in the center of the sack is suitably hydrated.
The patent to Dicker (U.S. Pat. No. 3,922,832) also discloses individual porous sacks of dry concrete mix as horizontal wall construction units. Insulating and acoustical fillers may also be used. Successive units are superimposed on each other in a sandbag-like arrangement. The units can be positioned before wetting or can be wet just prior to being laid. In hydrating these construction units the amount of water applied is based on the trained observations of the worker, who must not exceed a maximum amount which will cause a predetermined "slump" or spreading out of the construction unit.
Representative mat-like units are disclosed by U.S. Pat. Nos. 4,405,257 (Nielsen); 3,561,219 (Nishizawa et al); 3,837,169 (Lamberton) and 3,696,623 (Heine et al). Nielsen (U.S. Pat. No. 4,405,257) discloses a compartmentalized safety mat which may be filled with cement. The mat has an undulating or wavy surface with a checker board pattern of alternating domed and flat squares.
Nishizawa et al (U.S. Pat. No. 3,561,219) disclose a woven mat-like structure having adjacent, parallel, continuous tubular compartments filled by pumping in a slurry of water, sand and gravel. Concrete mix as filler is not taught, and consequently, the mats of Nishizawa et al lack required structural values for use as terranean building materials. According to Nishizawa et al, asphalt mats and concrete blocks have been used in bank revetment or coast protection works, but were found to be unsatisfactory from the point of view of working efficiency and mechanical properties.
Lamberton (U.S. Pat. No. 3,837,169) discloses an erosion control matress with elevated bulbous shaped structures. The matress comprises two sheets of flexible material with a plurality of cords interconnecting between the interior surfaces of the sheets. Concrete filler is continuous in the interior of the matress which is not compartmentalized, and therefore, should lack the desired flexural characteristics.
Heine et al (U.S. Pat. No. 3,696,623), like several others mentioned above relate to a structure employed in controlling erosion in waterways, shore lines, beaches, and lacks the required structural values needed for use as a unit of construction for roadways, building applications, supporting structures, and particularly in ply concrete construction. The woven mats of U.S. Pat. No. 3,696,623 comprise a network of open weave bags which are spaced from one another. The tubed mats are filled with thermoplastic materials.
Accordingly, it would be highly desirable to have a versatile concrete mat-like unit with improved structural values, including enhanced load bearing properties and resistance to fracturing achieved through ply concrete construction which adds flexural characteristics and residual strength to concrete bodies not otherwise attainable with poured concrete.